Penicillamine has already been made from 2,2,5,5-tetramethyl-thiazolidine-4-carbonitrile by converting the nitrile either directly or via the intermediate of the carbonamide into a tetramethyl-thiazolidine-4-carboxylic acid ester. The ester is then reacted with hydrochloric acid to form the hydrochloric acid salt of penicillamine and the penicillamine hydrochloride can then be neutralized with alkali to obtain the free acid (see Jahrbuch 1967 des Landesamtes fur Forschung Nordrhein-Westfalen, pages 11 to 35). This process however is complicated and expensive since it is necessary first to obtain the intermediate product, the carboxylic acid ester. Besides it results in only low yields. The direct conversion of the tetramethyl-thiazolidine-4-carbonitrile into a salt of pencillamine has not been possible heretofore.
It is therefore an object of the present invention to obtain penicillamine or a homolog thereof directly from a 2-disubstituted 5,5-dialkyl-thiazolidine-4-carbonitrile.